I have a Milwaukee pH51 pen. It's blue. I always store the pen in storage solution.
I put the pen in 7.0 calibration solution and adjusted the "7" screw until it read 7.0. No problem there. So then I rinsed it with tap water and put it in 4.0 solution and the meter reads 6.5 and no matter how many times i turn the "4" screw or what direction, it doesn't read below 6.4 pH in 4.0 solution.
Any suggestions?
I put the pen in 7.0 calibration solution and adjusted the "7" screw until it read 7.0. No problem there. So then I rinsed it with tap water and put it in 4.0 solution and the meter reads 6.5 and no matter how many times i turn the "4" screw or what direction, it doesn't read below 6.4 pH in 4.0 solution.
Any suggestions?